A prospective cohort study was conducted to evaluate the long-term effects of a high-fat diet on the incidence of colon cancer. The study participants were randomly selected from the population of interest. Dietary patterns were assessed through the use of periodic self-completed questionnaires. The investigators reported a 5-year relative risk of 1.60 for people who consumed a high-fat diet compared to individuals who consumed a low-fat diet. The 95% confidence interval was 1.02 to 2.15. This study is most likely to have which of the following p values?

Question

A prospective cohort study was conducted to evaluate the long-term effects of a high-fat diet on the incidence of colon cancer.  The study participants were randomly selected from the population of interest.  Dietary patterns were assessed through the use of periodic self-completed questionnaires.  The investigators reported a 5-year relative risk of 1.60 for people who consumed a high-fat diet compared to individuals who consumed a low-fat diet.  The 95% confidence interval was 1.02 to 2.15.  This study is most likely to have which of the following p values?

Quizplus · Accepted Answer

Relative risk (RR) is the probability of the outcome of interest occurring in the exposed group compared to the probability of it occurring in the non-exposed group. The null value of the RR is 1.0; a RR of 1.0 means that the outcome occurs with equal frequency in both groups and that there is no association between the exposure and the outcome. A RR > 1.0 means that the outcome occurs more frequently in the exposed group (positive association). The RR says nothing about the statistical significance of a study. Statistical significance can be expressed with either p values or confidence intervals, but both are interrelated. For instance, p < 0.05 corresponds to a 95% confidence interval that does not contain the null value. Likewise p < 0.01 is equivalent to a 99% confidence interval that does not contain the null value. Conversely, if the null value is within a given confidence interval, then the p value is > the equivalent confidence interval. > 11ec25c8_d23b_9635_bc81_17fc4191171b_MD0003_00 In general, for study results to be statistically significant, the 95% confidence interval must not contain the null value. This is equivalent to p < 0.05, which means that there is less than a 5% chance that the results are due to chance alone. In this case, the 95% confidence interval is 1.02 to 2.15 and does not contain the null value of 1.0. This corresponds to p < 0.05, thus 0.04 is the only correct answer choice. (Choices B, C, D, and E) These p values are all > 0.05, meaning the associated 95% confidence interval would contain the null value. Educational objective: Confidence intervals and p values are interrelated and express the statistical significance of a study. In a statistically significant study, p should be < 0.05. This corresponds to a 95% confidence interval that does not include the null value.

A Prospective Cohort Study Was Conducted to Evaluate the Long-Term